The present invention relates generally to disk drive control, and more particularly to a sync detection technique for properly detecting a predetermined bit sequence from a recording disk medium in which media flaws exist.
Recording of user data involves segmenting the data into blocks corresponding to tracks or sectors of a recording disk and writing a synchronization code at the starting point of each block. The user data is further divided into subblocks when a media flaw is discovered by a prescan test and the subblocks are spaced apart by a length sufficiently covering the detected flaw and a sync code is further attached to the subdivided data. When reading data from the disk, a reference bit sequence is generated and compared with the recorded sync code to detect proper timing for reading user data. With conventional disk drives, sync detection occurs only when there is a perfect bit-by-bit match between the recovered and reference bit sequences. However, small media flaws exist which are not detected by the prescan and due to the undiscovered flaws the recorded sync codes are disrupted, resulting in a failure to detect proper read timing. Such unfavorable Instances increase with the number of media flaws undetected by the prescan.